Methods are being developed to delineate the types of hearing losses associated with Osteogenesis Imperfecta (OI). Measurements of middle ear function by tympanometry and acoustic reflexes are being developed to classify penetrance and types of auditory deficits associated with differing forms of this disease. Current findings indicate that approximately half of the patients under 30 years of age and almost all of those over 30 years have sensorineural hearing losses. Although some patients with OI have a stiff middle ear system similar to that seen in otosclerosis, the majority have absent reflexes and increased compliance of the middle ear, with notched tympanograms suggestive of anomalous ossicular articulation. Similar findings in otherwise uninvolved relatives suggest a genetic basis for these defects.